André Augustinus

P2 events & perturbations

21 May 2010

ALICE Technical Coordination Meeting

André Augustinus

Overview 10.05 : Cooling water stop 11.05 : Water leak 18.05 : Power glitch

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

10.05 : cooling water stop 16:08, 16:24 – Power cut, affecting control of cooling

water• Stop of iced water production• Slow rise in temperature of mixed water

• CRs switched over to ‘backup cooling’ by CV piquet

~17:20 – Iced water restarted, cooling down• Running in degraded mode

~18:30 – All temperatures back to ~nominal 11.05 ~11:00 – Back to normal operation

• Caused minor perturbation in water temperatures

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

10.05 : cooling water stop

ALICE Technical Coordination Meeting 21 May 2010

16:08

17:20

Iced water

mixed water

Switchoverto backup

mixed water[return CR1]

Ambient CR1

André Augustinus

10.05 : cooling water stop Cause:

• Communication card in PLC lost due to power cuts Impact for ALICE:

• Increase of iced and mixed water temperatures (both CR and UX)• Reduced cooling efficiency; as usual, most remarkable in CR1• Water temperatures of dipole close to switch-off limit

Remarks:• Switchover to backup water for CRs had to be done manually

• Automatic switchover only on ‘no flow’, not on ‘high temperature’

Actions:• Modify logic for automatic switchover to backup (by EN/CV)

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

11.05 : water leak ~11:00 – A water leak in one of the racks in CR4 was

reported Intervention by P2 technicians to

stop the leaking purge

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

11.05 : water leak Cause:

• Leaking purge in rack CR4-X07 Impact for ALICE:

• Switch off of 2 racks for intervention (FMD and BCM, same power)• Water spilled on back of CAEN crate of BCM

• No further damage reported

Remarks:• Leak was spotted by somebody in CR4, but would also have triggered a water

leak detection by DSS• Stopping the (normal) power to the rack was in principle not sufficient, as most

equipment is on UPS (and would have caused major disruption when cut) Actions:

• Restart regular inspection tours• Procedure for intervention on UPS powered racks

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

18.05 : power glitch 05:35 : short power

glitch at P2 (and rest of CERN)

20% on 2-3 cycles Impact on most

accelerators (beams lost) and some experiments (ALICE and LHCb dipoles)

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus

18.05 : power glitch Cause:

• Perturbation on 400kV network supplying CERN (no details from RTE yet) Impact for ALICE:

• Dipole tripped off• No other impact reported

Remarks:• Relatively minor impact• Confusion on ramping up magnet

• CCC thought ALICE ramped up magnet• ‘Forgot’ to reset beam permit → Required additional ramp down - ramp up

Actions:• Again, strengthen procedure with CCC on ramping magnets• Automatic reset of beam permit by magnet safety system before ramp-up

ALICE Technical Coordination Meeting 21 May 2010

André Augustinus ALICE Technical Coordination Meeting 21 May 2010